Telemetry is a key element in any communication, sensor, or data transmission system. Simply stated, the design criteria of most telemetry systems are (a) the maximization of the amount of information or "data" that can be transmitted per unit time and (b) the minimization of attenuation of the transmitted data thereby minimizing power requirements for the transmitter element of the system. Additional design criteria include reliability, physical size, and costs to manufacture, maintain and operate.
Almost any type of communication, control, and sensor system uses some form of telemetry. Amplitude and frequency modulation of electromagnetic carrier radiation are the backbone of the communications industry. Numerous wireless and "hard wired" systems are used as telemetry links between devices such as remote control devices for door or gate openers and the control station from which control commands are initiated. Likewise, numerous wireless and hard wired telemetry systems are used to couple remote sensors such as electromagnetic, acoustic and nuclear sensing devices to equipment which controls the operation of these sensors, and which also converts the basic responses of these sensors into parameters of interest. Although almost endless in design and application, most telemetry systems share three basic elements: a modulator element, a demodulator element, and a telemetry link connecting the modulator and demodulator elements. The modulator converts the response of a sensor, or the output of a microphone, or the output of a television camera to some type of signal or data that can be transmitted over the telemetry communication link. The demodulator element receives the transmitted data and converts these data to the desired output which might be spoken words, or a video image, or a set of measurements in engineering units. The telemetry link can be an electromagnetic "wireless" link, or a "hard wired" link such as one or more electrical conductors, or one or more optical fibers.